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: http://www.naic.edu/~phil/aosoft/radardecode.html
Дата изменения: Thu Nov 4 00:00:09 2010 Дата индексирования: Tue Oct 2 06:51:30 2012 Кодировка: |
radardecode is a filter to decode radar data. The overlap save algorithm from THE FAST FOURIER TRANSFORM AND ITS APPLICATIONS (Brigham 1988 pg.212) is used. The input data is read from standard input (as a pipe), unpacked, transformed to the frequency domain, conjugated and then multiplied by the transformed code, transformed back to the time domain, and then the complex points are written to standard out as two 4 byte floating point numbers.
radardecode on startup will first allocate the buffers it needs and then it prepares the pn code. The program /usr/loca/bin/comppncode will be run to generate the pn code to use for decoding.
The input data can be ri, cbr, or unpacked data (depending on the -m option). The program will only process one polarization at a time.
If ri data is input, then the header must have been already be stripped off (see stripVme(1l). If the ri data had two polarizations, then one of them must be stripped off before inputting it to this program.
If cbr data is input then all polarizations are input to the program and the -p option is used to tell the number of polarizations input, and which polarization should be decoded.
For unpacked data, the input should be complex floating point numbers (one polarization only).
A number of shell scripts under ~phil/datatk/astro/rdrN have been written to drive the radardecode program (see radarranging(1l)).
The examples below show different ways of calling radardecode
Assume the data is from the ri and is on disc. The headers have already been stripped off. The data is 2 bit packed, one polarization, with a codelength of 8191. Add .5 to the input data and don't printout the time for each fft. Since the number of codes were not given, the program will decode until the end of file is hit or 100000000 codes have been decoded.
Assume the data is ri 8 bit data on disc, two polarizations, with the headers already removed. You want to decode the 1st (oc) polarization. The code is 2047 long and the decode fft length is 256k
Decode cbr data, 2 polarizations, 2 samples/baud, and keep the 1st polarization. The codelength is 64k-1. The output data will have 65535*2 range bins.
~phil/util/filters/radardecode.c location of source code /usr/S2local/bin/radardecode executable for sun ~phil/datatk/astro/rdrN/main_decode.sc shell scripts to drive radardecode. /usr/local/bin/comppncode program to compute pncodes for sun.
comppncode(1l),radarranging(1l)
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